| 211 |
|
Distributed ray-tracing performs anti-aliasing by randomly sampling |
| 212 |
|
over pixels. |
| 213 |
|
A value of one will randomly distribute samples over full |
| 214 |
< |
pixels. |
| 214 |
> |
pixels, and is not really recommended due to the tendency of |
| 215 |
> |
samples to (nearly) coincide. |
| 216 |
|
A value of zero samples pixel centers only. |
| 217 |
< |
A value between zero and one is usually best |
| 217 |
< |
for low-resolution images. |
| 217 |
> |
A value around 0.5-0.8 is typical. |
| 218 |
|
.TP |
| 219 |
|
.BI -pm \ frac |
| 220 |
|
Set the pixel motion blur to |
| 408 |
|
This is the maximum number of diffuse bounces computed by the indirect |
| 409 |
|
calculation. A value of zero implies no indirect calculation. |
| 410 |
|
.IP |
| 411 |
< |
In photon mapping mode (see |
| 411 |
> |
This value defaults to 1 in photon mapping mode (see |
| 412 |
|
.I -ap |
| 413 |
< |
below), a positive value implies that global photon irradiance is |
| 414 |
< |
always computed via |
| 413 |
> |
below), implying that global photon irradiance is always computed via |
| 414 |
|
.I one |
| 415 |
< |
ambient bounce. A negative value enables a preview mode that directly |
| 416 |
< |
visualises the irradiance from the global photon map without any ambient |
| 417 |
< |
bounces. |
| 415 |
> |
ambient bounce; this behaviour applies to any positive number of ambient |
| 416 |
> |
bounces, regardless of the actual value specified. A negative value enables |
| 417 |
> |
a preview mode that directly visualises the irradiance from the global |
| 418 |
> |
photon map without any ambient bounces. |
| 419 |
|
.TP |
| 420 |
|
.BI -ar \ res |
| 421 |
|
Set the ambient resolution to |
| 464 |
|
lost when the program finishes or dies. |
| 465 |
|
By using a file, different invocations can share illuminance |
| 466 |
|
values, saving time in the computation. |
| 467 |
< |
Also, by creating an ambient file during a low resolution rendering, |
| 468 |
< |
better results can be obtained in a second high resolution pass. |
| 467 |
> |
Also, by creating an ambient file during a low-resolution rendering, |
| 468 |
> |
better results can be obtained in a second high-resolution pass. |
| 469 |
> |
(It is a good idea to keep all of the calculation parameters the same, |
| 470 |
> |
changing only the dimensions of the output picture.)\0 |
| 471 |
|
The ambient file is in a machine-independent binary format |
| 472 |
|
which may be examined with |
| 473 |
|
.I lookamb(1). |
| 542 |
|
above), caustic photon irradiance is evaluated at primary rays, and |
| 543 |
|
indirect inscattering in |
| 544 |
|
.I mist |
| 545 |
< |
is accounted for by volume photons. |
| 545 |
> |
is accounted for by volume photons. Contribution photons are treated as |
| 546 |
> |
global photons by |
| 547 |
> |
.I rpict. |
| 548 |
|
.IP |
| 549 |
|
Additionally specifying |
| 550 |
|
.I bwidth2 |
| 561 |
|
is invariably looked up. |
| 562 |
|
.IP |
| 563 |
|
Using direct photons replaces the direct calculation with density estimates |
| 564 |
< |
for debugging and validation of photon emission. |
| 564 |
> |
for debugging and validation of photon emission. |
| 565 |
|
.TP |
| 566 |
|
.BI -am " frac" |
| 567 |
< |
Coefficient for maximum search radius for photon map lookups. The search |
| 568 |
< |
radius is automatically determined based on the average photon distance to the |
| 569 |
< |
distribution's centre of gravity, and scaled by this coefficient. Increase this |
| 570 |
< |
value if multiple warnings about short photon lookups are issued. |
| 567 |
> |
Maximum search radius for photon map lookups. Without this option, an |
| 568 |
> |
initial maximum search radius is estimated for each photon map from the |
| 569 |
> |
average photon distance to the distribution's centre of gravity. It is then |
| 570 |
> |
adapted to the photon density in subsequent lookups. This option imposes a |
| 571 |
> |
global fixed maximum search radius for |
| 572 |
> |
.I all |
| 573 |
> |
photon maps, thus defeating the automatic adaptation. It is useful when |
| 574 |
> |
multiple warnings about short photon lookups are issued. Note that this |
| 575 |
> |
option does not conflict with the bandwidth specified with the |
| 576 |
> |
.I \-ap |
| 577 |
> |
option; the number of photons found will not exceed the latter, but may be |
| 578 |
> |
lower if the maximum search radius contains fewer photons, thus resulting in |
| 579 |
> |
short lookups. Setting this radius too large, on the other hand, may |
| 580 |
> |
degrade performance. |
| 581 |
|
.TP |
| 582 |
+ |
.BI -ac " pagesize" |
| 583 |
+ |
Set the photon cache page size when using out-of-core photon mapping. The |
| 584 |
+ |
photon cache reduces disk I/O incurred by on-demand loading (paging) of |
| 585 |
+ |
photons, and thus increases performance. This |
| 586 |
+ |
is expressed as a (float) multiple of the density estimate bandwidth |
| 587 |
+ |
specified with |
| 588 |
+ |
.I \-ap |
| 589 |
+ |
under the assumption that photon lookups are local to a cache page. Cache |
| 590 |
+ |
performance is sensitive to this parameter: larger pagesizes will reduce the |
| 591 |
+ |
paging frequency at the expense of higher latency when paging does occur. |
| 592 |
+ |
Sensible values are in the range 4 (default) to 16. |
| 593 |
+ |
.TP |
| 594 |
+ |
.BI -aC " cachesize" |
| 595 |
+ |
Set the total number of photons cached when using out-of-core photon |
| 596 |
+ |
mapping, taking into account the pagesize specified by |
| 597 |
+ |
.I \-ac. |
| 598 |
+ |
Note that this is approximate as the number of cache pages is rounded to |
| 599 |
+ |
the nearest prime. This allows adapting the cache to the available physical |
| 600 |
+ |
memory. Cache performance is less sensitive to this parameter, and reasonable |
| 601 |
+ |
performance can obtained with as few as 10k photons. The default is 1M. This |
| 602 |
+ |
option recognises multiplier suffixes (k = 1e3, M = 1e6), both in upper and |
| 603 |
+ |
lower case. |
| 604 |
+ |
.TP |
| 605 |
|
.BI -me " rext gext bext" |
| 606 |
|
Set the global medium extinction coefficient to the indicated color, |
| 607 |
|
in units of 1/distance (distance in world coordinates). |
| 664 |
|
termination, and the |
| 665 |
|
.I -lw |
| 666 |
|
setting (below) must be positive. |
| 667 |
< |
If N is a negative integer, then this sets the upper limit |
| 668 |
< |
of reflections past which Russian roulette will be used. |
| 667 |
> |
If N is a negative integer, then this limits the maximum |
| 668 |
> |
number of reflections even with Russian roulette. |
| 669 |
|
In scenes with dielectrics and total internal reflection, |
| 670 |
|
a setting of 0 (no limit) may cause a stack overflow. |
| 671 |
|
.TP |
| 912 |
|
Greg Ward |
| 913 |
|
.SH "SEE ALSO" |
| 914 |
|
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pdfblur(1), pfilt(1), |
| 915 |
< |
pinterp(1), pmblur(1), printf(3), ra_rgbe(1), rad(1), rtrace(1), rvu(1) |
| 879 |
< |
|
| 915 |
> |
pinterp(1), pmblur(1), printf(3), ra_rgbe(1), rad(1), rpiece(1), rtpict(1), rtrace(1), rvu(1) |
